The flying robot TubRob has been built in the framework
of student project courses for participation in an competition,
the International
Aerial Robotics Competetion. Development began in October
1992 and lasted till the date of the competition in the summer
of 1995.

2
Competition

The Association
for Unmanned Vehicle Systems annually organizes a competion
for flying robots, which is open to university teams. In the
year of 1995, the task was to collect six metal disks randomly
distributed in a 2 m circle, transport them one after the other
across a barrier and drop them in the target area.

Things permitted:

Things prohibited:

Autonomous aerial robots

Control devices onboard and/or at a ground station

Wireless communication between robot and ground station

Sensor components on the ground

Human interference once the mission has begun

Touching the ground during the Mission

Wires and cables between the robot and the ground

3
TubRob

TubRob is a blimp filled with helium, 2.5 meters in diameter.
It is propelled by six electric engines. Computational power
is located both onboard (two microcontrollers) and on the ground
(one PC and one microcontroller). The blimp and the ground
station communicate via a radio link. Further principal components
are an ultrasonic positioning system, an ultrasonic altimeter,
an electronic compass and the gripper for acquiring the disks.
The highlights are presented in greater detail below.

Positioning System
A circular ultrasonic transmitter consisting of twelve ultrasonic
transducers by Polaroid is located onboard. Eight receivers are
positioned at the border line of the competition arena such that
at least three of them will always receive a signal from the
transmitter. Time-of-flight calculation gives circular base lines
relative to each of the receivers. The blimp's position within
the arena is determined through triangulation. The system is
accurate to a few centimeters over the whole arena, which is
20 m times 40 m in size.

Software
The four computers involved cooperate on the task of guiding
the blimp according to the variety of sensor data. Every computer
runs different specialized processes. A carefully tailored real
time multi-tasking system takes care of invoking the respective
routines in time and implements the communication among the processes
and the computers. The majority of sensor data are generated
onboard and are, therefore, processed at that place. Fuzzy controllers
calculate suitable revolutions-per-minute figures for the engines
and control their accomplishment. A primary task of the ground
station is to provide a user interface for both visualizing the
robot's state and allowing manual interference (e.g. take-off,
emergeny landing, manual override of parts of the control hierarchy
for test purposes).

4
Results

As early as April 1995, a TubRob prototype presented at the Berlin
booth at the Hannover Industrial Fair attracted considerable
attention. The final version took the second place in the
copetition in Juli 1995 in Atlanta, Georgia. Only Standford University
came in ahead, while others, like MIT, were surpassed. Besides
this measurable success, having been involved in such an extensive
project - which actually succeeded - was a great and valuable
experience to the contributers.

After the competition TubRob was shown at the exhibition on
the occasion of TU Berlin's 50th anniversary and at the "Feast
of Ideas" (Fest der Ideen) initiated in September 1997 by
the President of the Federal Republic of Germany.

5
People

David Hanisch, Olaf Kubitz, Marek
Musial, Martin Schlicker, Robert Scholz, and Roland
Stenzel were the students being involved in the project all the
way from the start to the end. Further contributers were Burckhardt
Bonello, Giorgio Brasachhio, Knut Dalkowski, Thomas Dietrich,
Jürgen Focke, Peter Gober, Robert Junghans, Reinhard Koehn,
Bernd Krünelke, and Steffen Müller. Engaged as supervisors
and teachers were Wolfgang
Brandenburg and Marion Finke.